Autotaxin (ATX) is a secreted enzyme of the ectonucleotide pyrophosphatase/phosphodiesterase family, and is also known as Ectonucleotide Pyrophosphatase/Phosphodiesterase 2 (ENPP-2 or NPP2). ATX plays a role in driving pathological conditions, including fibrosis, arthritic inflammation, neurodegeneration, neuropathic pain, and cancer. ATX is the fundamental regulator of the conversion of Lysophosphatidylcholine (LPC) to Lysophosphatidic Acid (LPA). LPA is a bioactive lipid that affects migration, proliferation, and survival of various cell types.
Inhibition of ATX has been shown to reduce LPA levels in pathological settings. Reduction of LPA may provide therapeutic benefits in diseases with unmet medical need, including cancer, lymphocyte homing, chronic inflammation, neuropathic pain, fibrotic diseases such as Idiopathic Pulmonary Fibrosis (IPF), thrombosis, and cholestatic pruritus which are caused, mediated and/or propagated by increased LPA levels and/or activation of ATX.
Fibrotic diseases are chronic, debilitating and often lethal pathologies driven by a dysregulated response to tissue or organ injury. Fibrosis can develop in the liver, kidney, lung, dermis, vasculature, gut and other sites. Fibrosis develops due to action of pathways including growth factors, cytokines, integrin and lipids.
ATX, LPA, and LPA Receptor (LPAR) pathways have been implicated in fibrotic disease. For example, profiling studies show increased levels of ATX, LPA and LPARs in various rodent models of fibrosis and in human patient fluids and biopsy tissue. LPA can induce proliferative, survival, and chemotactic responses in transformed cell lines, indicating that LPA may exert pro-inflammatory and pro-fibrotic responses in cells known to be critical in fibrotic disease, including: fibroblasts, smooth muscle cells, macrophages, epithelial and endothelial cells, and leukocytes. Gene-targeted mouse models have implicated LPARs in fibrosis pathogenesis. Inhibitors of LPARs indicate that antagonism of receptors within this pathway blocked or reversed fibrosis in the lung, liver, kidney and skin in rodents. Cell type-specific gene targeting studies have showed that ATX plays a role in the development of lung fibrosis and inflammatory arthritis.
ATX and LPA have also been implicated in tumor progression and metastasis. ATX may be responsible for increased LPA levels in ascites and plasma of ovarian cancer patients since ATX converts LPC to LPA. Increased levels of LPA, altered receptor expression and altered responses to LPA may contribute to initiation, progression or outcome of ovarian cancer. LPA has also been linked to prostate, breast, melanoma, head and neck, bowel, brain and thyroid cancers.
LPA has been shown to promote tumor cell survival, proliferation, invasion and migration into neighboring tissues, which can result in the formation of metastases. Additionally, LPA promotes cytoskeletal remodeling that may enhance migratory and invasive properties of cells, which may contribute to cancer metastasis. These biological and pathobiological processes of LPA are initiated through the activation of G-protein coupled receptors.
Transcriptome analyses of more than 350 normal tissues and more than 1700 malignant tissues demonstrate that ATX is expressed in a variety of carcinomas and sarcomas, underscoring the potential contribution of LPA to metastatic disease.
Accordingly, when treating patients with diseases, such as cancer, lymphocyte homing, chronic inflammation, neuropathic pain, fibrotic diseases, thrombosis, and cholestatic pruritus it is desirable to lower LPA levels. This can be accomplished through inhibition of enzymes involved in LPA biosynthesis, such as ATX.
Since ATX is expressed in tumors and affects tumor cell proliferation and invasion into neighboring tissues both of which can lead to the formation of metastases, ATX is a target for anti-tumor therapy. Moreover, in angiogenesis, ATX, taken with other anti-angiogenetic factors, brings about blood vessel formation. Angiogenesis supplies tumors with nutrients during tumor growth. Therefore, inhibition of angiogenesis is a target for anti-tumor therapy, leading to starvation of a tumor.
ATX has also been implicated in nerve injury-induced neuropathic pain. LPA biosynthesis, through ATX, is the source of LPA for LPA1 receptor-mediated neuropathic pain. Therefore, targeted inhibition of ATX-mediated LPA biosynthesis may represent a novel treatment to prevent nerve injury-induced neuropathic pain.
Various publications refer to compounds that are capable of inhibiting ATX, including: WO2013061297, WO2012166415, US20120100592, WO2012024620, WO2011116867, WO2011017350, WO2011006569, WO2010115491, WO2010115491, WO2010112124, WO2010112116, WO2010063352, US20100016258, and WO2009151644.
Accordingly, there remains a need for ATX inhibitors having the potential to reach the clinic and obtain regulatory approval for use in the treatment and/or prophylaxis of physiological and/or pathophysiological conditions, such as cancer, lymphocyte homing, chronic inflammation, neuropathic pain, fibrotic diseases, thrombosis, and cholestatic pruritus which are caused, mediated and/or propagated by increased LPA levels and/or the activation of ATX.